Evaluating microgen GN A + B-ID versus API 20E for the identification of Salmonella spp. in food

This study assessed the performance of the Microgen GN A + B-ID system for identifying Salmonella spp. by comparing it with the API 20E method using 284 strains isolated from food. All 284 strains were identified as Salmonella spp. by both systems, showing perfect genus-level concordance. However, in 21 strains (7.4%), the Microgen GN A + B-ID system showed biochemical reaction profiles that differed from those obtained with API 20E. Further investigation using conventional biochemical methods indicated that these discrepancies were associated with the GN B strip, a complementary component of the system designed to assess additional biochemical reactions, which showed false-negative results for inositol, rhamnose, and sorbitol, and a false-positive result for arginine. In this study, the Microgen GN A + B-ID system showed genus-level identification performance comparable to that of API 20E. The GN A strip alone proved sufficient for genus-level identification, whereas combining it with the GN B strip provides more comprehensive biochemical data but requires careful interpretation due to the risk of discrepant reactions in specific tests.